Nobel for explaining nature's protein factories

Three biochemists who revealed the secrets of ribosomes, the "protein factories" in all living cells, have shared this year's Nobel prize for chemistry.

Without ribosomes, it would be impossible for the information we inherit in DNA to be made into the proteins that make up all living things, from the tissues of the human brain to the keratin in hair and toenails.

Thanks to the winners' detailed studies of ribosome structure, biologists now know exactly how ribosomes manufacture individual proteins by "reading" the chemical recipes for them encoded in genes.

They also discovered a ribosomal "fact-checker" which explains why nature produces so few faulty proteins, and revealed how some antibiotics foil bacteria by sabotaging their ribosomes. Their research is now leading to new antibiotics that could help thwart hospital "superbugs", such as MRSA or methacillin-resistant Staphylococcus aureus .

Three-way split

The prize was split three ways between Venkatraman Ramakrishnan of the UK Medical Research Council's Laboratory of Molecular Biology in Cambridge, Thomas Steitz of Yale University and Ada Yonath of the Weizmann Institute of Science in Rehovot, Israel.

The 2009 prize builds on earlier discoveries about how genes work recognised in two previous Nobels. The first famously went in 1962 to Francis Crick, James Watson and Maurice Wilkins for their ground-breaking discovery of the structure of DNA itself.

The second, in 2006, went to Roger Kornberg for discovering how information in DNA is first copied into messenger RNA whenever a gene is active, and how this mRNA is then ferried across the cell to a ribosome. Here, the corresponding protein can be made by "reading" the gene recipe encoded initially in the DNA, then copied into mRNA.

Life's story

This year's winners took life's story a stage further by showing in minute detail how the ribosome actually reads the mRNA and decodes the information in it to manufacture a completely new protein, amino acid by amino acid.

To do this, they first had to establish the chemical structure of a ribosome, a massive molecule comprising two components: alarge and a small subunit. The mRNA is fed in through the small subunit, and the protein assembled and fed out through its larger counterpart.

Ada Yonath set the ball rolling in the late 1970s by focusing on the ribosomes from bacteria which live in unusually harsh environments. To thrive in such conditions, she reasoned, they would need the most structurally stable ribosomes, and so would hold their structures better when made into crystals, a necessary step towards investigating their structure through a form of analysis called X-ray crystallography.

Hot springs

First, she tried with a species that lives in hot springs, but she had more success with Haloarcula marismortui, a salt-tolerant species unique to the salt-choked Dead Sea.

By the early 1990s, Steitz and Ramakrishnan had joined the race, and Steitz finally cracked the problem by combining X-ray crystallography with detailed photos of ribosomes taken with electron microscopes.

In 1998, Steitz published the first crystal structure of the ribosome's large subunit, although it didn't include the positions of individual atoms.

Dead Sea

The entire picture arrived in 2000, when Steiz established the full structure of the large subunit from the Dead Sea bacterium, and Yonath and Ramakrishnan determined the structure of the small subunit in another heat-tolerant bacterium.

After that Ramakrishnan discovered a molecular ruler within the ribosome which checks that the mRNA as it is being read to ensure the correct protein is being loaded. This restricts errors to just one per 100,000 amino acids.

Since then, all the winners have shown in detail how individual antibiotics bind to and disrupt the ribosomes in bacteria. These same investigations have shed light on how some bacteria become resistant to these antibiotics, and how new ones might be made to overcome this.

"Scientists around the world are using the winners' research to develop new antibiotics that can be used in the ongoing battle against antibiotic-resistant microbes that cause so much illness, suffering and death," says Thomas Lane, president of the American Chemical Society.

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